What could cause a burning sensation under the skin on the back?

Neurodermatitis: An itchy back without a rash can be caused by a irritated small nerve fiber .The condition is called notalgia parasthetica. There is no test to diagnose this condition. It can be treated with topical medications or localized injections.

NotalgiaParesthetica: What you describe sounds like "notalgia paresthetica". It is usually caused by irritation of nerve roots as they exit the spine. The most common problem is poor posture and slouching. I recommend postural exercises and muscle strengthening to my patients with this problem. It does work. To be certain of what you are experiencing, i would see a dermatologist or your pcp first.